<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8" />
		<title>Document</title>
	</head>
	
	<body>
		<script type="text/javascript" >
			let arr = [1,3,5,7,9]

			//map专门用于加工数组，map方法会返回一个新数组，map方法不会修改原数组
			let arr2 = arr.map((item,index)=>{
				return item + 1
			})
			console.log(arr2)
			console.log(arr)


			function test(a){
				if(a === 1){
					return 100
				}
				return 99
			}
			test()

		</script>
	</body>
</html>